1. Field of the Invention
The present invention relates to a lithium ion conductive inorganic substance, in particular to a lithium ion conductive inorganic substance which is favorably used for solid electrolytes of lithium ion secondary batteries, partition walls of lithium air batteries and lithium seawater batteries, etc.
2. Related Art
All-solid batteries, using an inorganic solid electrolyte and not using organic substance even in electrodes, are free from worries about leakage of organic electrolyte or gas generated from organic electrolyte, and therefore are expected to be safe batteries. The all-solid batteries are less likely to induce a side reaction other than battery reactions compared to liquid batteries, and therefore are expected to have a longer operating life compared to liquid batteries.
In an example of the all-solid batteries, a positive electrode layer and a negative electrode layer are respectively laminated and sintered on both sides of a solid electrolyte layer, and an inorganic substance with lithium ion conductivity is used as a solid electrolyte which is included in the solid electrolyte layer, the positive electrode layer, and the negative electrode layer.
In addition, lithium air batteries and lithium seawater batteries, where a lithium compound is used at negative electrode side and a catalyst is disposed at positive electrode side, are in principle not limited for their capacity by their positive electrodes; therefore, it is expected that smaller batteries with larger capacity can be formed therefrom. Lithium ion conductive inorganic substances are also used in partition walls of the lithium air batteries and lithium seawater batteries.
Here, Patent Document 1 discloses a lithium ion secondary battery using a glass ceramics that contains a crystal with a crystal structure the same as that of LATP (Li1.3Al0.3Ti1.7(PO4)3) crystal, as a lithium ion conductive inorganic substance to construct a solid electrolyte layer in order to enhance ion conductivity and chemical stability of the solid electrolyte layer.
Patent Document 2 also discloses a lithium air battery using a glass ceramics that contains LATP (Li1.3Al0.3Ti1.7(PO4)3) as a lithium ion conductive inorganic substance to construct a partition wall in order to enhance ion conductivity and chemical stability of the partition wall (waterproof layer).
Non-Patent Document 1 also discloses a lithium ion secondary battery using an inorganic substance where a portion of the Li in LZP (LiZr(PO4)3) with a crystal structure different from that of LATP is substituted with Sc as a lithium ion conductive inorganic substance to construct the solid electrolyte.    Patent Document 1 Japanese Unexamined Patent Application, Publication No. 2007-134305    Patent Document 2 Japanese Unexamined Patent Application, Publication No. 2010-192313    Non-Patent Document 1 T. Salkus, and five others, “Synthesis, structure, and electric properties of Li1+xScxZr2−x(PO4)3 (x=0.1, 0.2, 0.3) ceramics”, Lithuanian Journal of Physics, 2006, vol. 46, No. 3, pp. 361-365.